Pavement compositions and method of making the same



Patented Aug. 18, 1936 PATENT OFFICE,

PAVEMENT COMPOSITIONS AND METHOD OF MAKING THE SAME William L. Schloss, Cleveland Heights, Ohio No Drawing. Application July 28, 1932,

Serial No. 625,544

6 Claims. (01. 106-31) This application is a continuation in part of my former application for patent for Paving composition, filed April 26th, 1927, Serial No. 186,828.

The invention relates to paving material and the method of making the same and has for its generalobject the provision of a novel asphaltio vibrations incident to service or of climatic conditions.

ever, a drawback to numerous types of paveinevitable under modern heavy traflic conditions.

:It is with the above facts in view that I have done considerable experimentation in the endeavor to overcome the difficulties and as the result of numerous tests I have devised the present invention which contemplates the provision of a paving composition embodying, as the result of my discovery, the conventional materials such as trap rock or its equivalent, screenings, chips or the like, sand and a bituminous binder plus a reasonably small percentage of finely divided iron ore of the type containing iron oxide, the entire mass possessing by actual test a pressure withstanding characteristic far superior to ordinary compositions.

Another object of the invention is to provide a paving composition in which the percentage of finely divided iron oxide containing ore may be varied within considerable limits depending upon the proportion of iron oxide therein, it being well known that certain ores are richer in oxide than others, this fact entailing a flexibility in the range so that a greater or less amount of the ore may be used dependent upon its iron oxide content.

Yet anotherobject of the invention is to pro vide a composition of this character particularly adapted for paving and analogous purposes which may be of the hot or cold mixed type depending upon the character of the bituminous binder employed and depending upon whether fluidity or 5 plasticity is attained by means of heat or is to be obtained by the presence or addition of a solvent, flux, vehicle or the like, which auxiliary substance Would logically be of a type capable of dissipation after laying of the pavement so that 10 the material constituting the same will solidify and become a hard impenetrable mass.

A further object of the invention is to provide a novel method of mixing the ingredients to form the pavement, the method involving a preliml5- inary coating of the larger or heavier rock fragments so as to facilitate and insure adhesion thereto and cohesion thereof with the binder in either the cold or hot type of mix, this feature precluding the mere embedding of the fragments 20 within the plastic binder withoutadhesion, as adhesion and consequent homogeneity in the resultant mass will be positively assured.

Another object of the invention is to provide a composition which may be substantially the same in so far as the content of iron oxide is concerned regardless of whether it be employed as the lower or binder layer or the upper or surface layer mixture, it being logical that a considerable reduction in the iron oxide content be made in producing the finishing or top layer or dressing for a roadway or the like.

To the attainment of the foregoing and other objects and advantages, the invention preferably consists in the mixes, proportions of ingredients under difierent circumstances and fordiiferent purposes, and the method steps to be hereinafter more fully described and claimed.

In carrying out the invention I contemplate providing a composition which comprises, broad- 1y, a physicalmixture of broken rock of suitable size and type, screenings or chips of the same or a different rock, sand, a bituminous binder and iron oxide in a form occurring in nature as incorporated in iron ore. In the actual carrying 45 out of the invention, the purpose of the specific mixture as made up must be considered as having a bearing on the size of the rock fragments and the proportion of iron oxide and the asphaltic cement or bituminous material used as a binder. 50 For instance, the base layer is naturally made of larger pieces of rock and probably a smaller percentage of asphaltic cement than the mixture used as the surface, it being also clear that no large fragments whatsoever are used for'the top 55 or finishing coat. Many wide variations may be resorted to within the purview of the invention but for purposes of illustration I will give certain definite figures.

Take for example a composition for the building of the lowermost layer or body of a pavement intended as a roadway, which layer is adapted to be laid upon a base which has been properly cleaned and swept and brought to line and grade. I prefer to make this foundation layer of broken rock aggregate ranging in size from pieces 1 and inches down to inch, this material being washed to remove all objectionable foreign matter and being dried before use. This aggregate may be made up say from 40 to 65% of pieces of rock ranging from 1 and inch to inch, 10 to 30% of pieces ranging between inch and inch, 5 to 15% of pieces ranging between and inch, and 5 to 8% of inch pieces or screenings. These diiferent masses separately preferably by some means equipped with a counterbalance for the weight of the container into which they are placed. The coarser material is placed in a mixing machine preferably of the pug mill type. A liquefier, which is a temporary and volatile solvent and which may consist of petroleum naphtha having an overpoint of approximately 225 F. and a dry point of approximately 450 F., or even commercial kerosene oil as a substitute, is then introduced within the mixer by spraying it onto the stone, only sufficient liquefier being added to each batch for properly and effectually coating the stone fragments. To this is then added from approximately 4.5% to 6.5% of an asphaltic cement or bituminous matter previously heated to between This asphaltic approximately 250 and 275 F. material may be prepared from natural lake or native oils having an asphaltic base and is refined by the known steam process and fluxed with petroleum oil to produce the desired consistency. It is intended that the asphalt shall be homogeneous, free from water, shall not foam when heated to 347 F., shall have a minimum specific gravity of 1.01 at 77 F., shall have a flash point not less than 347 F., shall have a melting point ranging between F. and 131 F., shall also have a penetration at 77 F. of gr. per five seconds, shall have an evaporation loss at 325 F. of a maximum of 1% in five hours, shall have a minimum bitumen content soluble in carbon bisulphide of 99%, shall contain but from 0.2 to 0.5% of insoluble inorganic matter and shall have a minimum ductility at 77 F. of 50 cm. While these characteristics may be varied to a certain extent they do seem to indicate the most efficient asphalt for the purpose. After the coarse aggregate has been sprayed with theliquefier as above mentioned the asphalt preferably answering the foregoing specifications is heated as stated and mixed with the mineral aggregate until each part thereof is thoroughly coated during the operation of the pug mill. The fine material is next incorporated within the mixture by even distribution the full length of the mixer. The next step is the addition to the mixture of say from 3 to 5% of iron oxide. This substance occurs in nature as part of certain kinds of iron ore and in some ores there is a much higher content of iron oxide than in others. The oxide content of any particular ore in question must of course be ascertained and a sufficient quantity of ore, according to its percentage of oxide content, is added to the mixer to introduce within the mixture an amount of iron oxide ap- /4, inch 7 30%,.and inch 3 to 12%. are weighed proximating from 3 to 5% of the mass. The pug mill is operated, that is to say the blades thereof rotated in the usual manner, to effect thorough mixing of the batch and the operation is continued until the resultant product is uniform as regards the distribution of the mineral aggregate throughout the mass.

The mixture having been made as described is laid in a manner well known to road builders in a layer of desired depth, is raked and then rolled to effect solidification.

The surface mixture to be placed on the foundation layer is produced in the same manner but the larger pieces of broken rock are omitted. In making the composition. for this second layer it is preferable to make use of broken rock or fragments ranging in size say from inch to inch 40 to 65%, betweerr and inch 10 to The liquefier used for coating the rock fragments, chips or screenings may range, as above described,- from .5 to

1%. The asphaltic cement content may inthis instance be slightly increased and may range from 6 to 7% while the iron oxide'content may be the same, namely 3 to 5%. The mixing of the material for this second or upper layer is carried out in the same Way as described in connection with the foundation layer. The second layer is laid in the customary manner, and packed by rolling, tamping or other means.

As a finishing coat or top mixture use is made of only the finest screenings or rock, say inch size and this ingredient will constitute from 94 to 99% of the mass. The quantity of liquefier is slightly reduced, ranging say from .4 to 1%. The asphaltic cement content may conveniently range between 2 to 5% and the amount of iron oxide need not exceed a range of from .1 to .5%.-

This aggregate for the top surface is prepared in the same manner as the others and applied in the customary mannerr Regardless of which for it will be observed that in each instance there is a very appreciable iron oxide content.

It should be understood that while iron oxide as. such might be used, it is preferably obtainable as naturally present in iron. ore. Obviously the crushed ore contains sand which is mentioned as one of the ingredients in the forepart of this description and this has no deleterious effect but.

' It may be interesting to know that actual tests have been made to determine the relative strength of asphaltic pavements which have and,

which do not have iron oxide as an ingredient. Samples of asphalt surfacing of the same area and thickness were subjected to compression,

tests, all tests being made at the same temperature, namely 72 F. asphalt withstood a stress of 690 pounds per square inch, that sheet asphalt with iron oxide added withstood a stress of 748 pounds per,

square inch, that ordinary asphalt concrete withstood a stress of 1608 pounds per square inch While asphaltic concrete with iron oxide incorlayer is being prepared If the iron ore contains but It was found that sheet.

porated therein withstood a stress of as much as 1775 pounds per square inch. These figures ascertained from actual tests clearly prove the added strength and durability resulting from the employment of a mixture in. accordance with my invention. It also seems that a pavement constructed as I contemplate has a great tenacity or freedom from brittleness and is, moreover, highly impervious and consequently not subject to deterioration under adverse climatic conditions.

From the foregoing description it will be apparent that I have thus provided a novel and improved composition for paving and analogous purposes which may be prepared easily and without greater expense than the ordinary varieties, which may be handled with equal ease and which will yet possess the numerous advantages previously set forth.

While I have described the preferred embodiment of the invention as carried out for the preparation of diiferent strata in paving operations and have mentioned certain definite ranges it should be understood that a certain latitude of variation is permissible and that I reserve the right to make whatever changes fall within the spirit of the invention and the scope of the claims hereunto appended.

Having thus described the invention, I claim:

1. A paving composition comprising broken rock including pieces of various sizes to 80%, a liquefier coating the rock pieces .5 to 1%, asphalt cement 4 to 7% and asufiicient amount of finely divided ore containing iron oxide to supply from 3 to 5% iron oxide to the mixture.

2. A paving composition comprising a mineral aggregate formed of rock fragments of progressively decreasing sizes totalling from to 87%, a petroleum product coating the rock pieces, as-

phaltic cement ranging from a minimum of 2 to a maximum of 7%, and iron oxide, in the form of natural iron oxide bearing ore, ranging from approximately 3 to 5%.

3. A paving composition comprising a mineral aggregate including rock fragments of varying sizes individually coated with a petroleum oil acting as a solvent for asphalt, said rock constituting from 60 to an excess of 90%, asphalt cement ranging between 2 and 7% and between .1 of 1% to 5% of iron oxide contained within natural ore.

4. A composition for paving, comprising relatively large pieces of broken rock from 40 to smaller pieces of broken rock 10 to 30%, still finer pieces of broken rock from 10 to 23%, an

asphalt liquefier for coating the rock pieces, as-

phaltic cement ranging from about 4.5 to 7% and from 3 to 5% of iron oxide to form an oxide bearing natural ore in a finely divided state.

5. The method of making a composition suitable for paving, comprising taking rock fragments of various sizes and placing them within a mixer, coating the rock pieces with a petroleum product acting as a solvent for asphalt, adding to the coated rock pieces melted asphalt, mixing the mass and adding to the mixture and intermingling therewith iron oxide in the form of finely divided oxide bearing ore.

6. The method of making a paving composition comprising taking from between 60 to 87% rock pieces of varying sizes, spraying them with a coating of a petroleum product acting as a solvent for asphalt, adding a mass of from about 4.5 to 7% of asphaltic cement, mixing the mass and mixing therein from 3 to 5% of iron oxide in the form of finely divided ore.

WILLIAM L. SCHLOSS. 

